You've got the basics listed, but there are a lot of variables. Stock ground isn't always the best ground available. Some stock grounds used with aftermrket systems add noise.. In my old 330Ci, the main power lead from the battery in the trunk ran up one side of the (forgot which side), so it was best not to run any speaker wires up that side to avoid adding noise to the system. Using stock speaker mounts, especially if they're the kind that attach to the door card and not...

First mistake: it's high amperage that dangerous, not voltage. Read this to learn more: http://gizmodo.com/5262971/giz-explains-how-electrocution-really-kills-youMy original advice was for a regular turntable. You're obviously unfamiliar, otherwise you'd know how easy it is to ground these. When it was revealed to be a console, I said it wasn't worth any repair. But if it's what the girlfriend wants, then logic is irrelevant.